What I would consider to be hacking one of these services is something along the lines of cracking databases (or I think what would be databases). In reality, I have no idea how sites like these store passwords. From what I read a little bit ago, sites such as these with massive databases don't story every thing in one place, which is good for two reasons in my opinion. A) when millions of people are accessing these databases, it helps to spread out the load, and doesn't bottleneck the host of the database, and B) this provides a step of security so that if one database is compromised, not every one is, or it makes it more difficult to gather all of the data at the same time.
If someone attempts to look up
how to hack facebook, they will only see things such as keyloggers. Why, though? I am sure that this is possible (even if highly impractical), and that someone somewhere would benefit from something like this. I know that these major companies have the money to sue anyone to death who did anything like this, but why hasn't it been done by a hacker yet? (If it has and I didn't realize it, I apologize).
In the end, what makes Facebook not hackable, or at least difficult? In reality it is not bulletproof, because nothing is ever 100% secure. I am sure some people could find this very profitable. Why hasn't this already happened, though? What kind of security measures are these companies taking to prevent things like this?